Human infection with a parasite called larva migrans visceralis (most often larva of Toxocara canis) has been poorly studied. In order to determine the extensity of infection in dogs, stray dogs at the age more than 1 year were studied. During section, the worms were found in 16 (11.3%) dogs, at the intensity of infection 2-12 specimens per dog, mean value 5.7. To estimate the extent of infection of soil through dog feces, and to find ways and vectors of toxocarosis, soil samples were studied, taken from house gardens, parks, lawns and places of children play. The eggs of T. canis were found in 7.3% samples. The soil from house gardens was infected in 8.1%, that from the places of children play – in 5.7%. The eggs of T. canis were most often found in samples collected in summer-autumn. Patients with clinical symptoms suggesting presence of larvae migrans visceralis were immunologically tested. Blood of 739 patients with various alergy symptoms or unclear ethiology was examined. The reaction was positive in 11,5% persons, most of them children at the age of 1-3 years. In 21 children aged 1 or less the titre was high. Because the children below 1 have a limited contact with soil, a possibility of passive infection through the placenta was considered. Using ELISA test, 100 pregnant women, and children during the first year of their life were examined. Antibodies against T. canis were found in 21 women (4.7%). During the birth, the antibodies were found in blood of one child only.